Recently magnetic resonance imaging (MRI) was commercially introduced to the medical field. MRI is a three dimensional imaging process. MRI is advantageous over other imaging procedures such as two dimensional and three dimensional CT X-ray techniques in that MRI better defines soft tissue structures. It is also advantageous over X-ray techniques, because it does not require the patient being exposed to X-rays.
The likelihood of an accurate diagnosis and assessment of therapeutic impact may be improved in MRI by the use of a contrast enhancement agent. At present, only ionic and nonionic forms of gadolinium based paramagnetic products which must be injected and so are invasive are authorized for use as a contrast enhancement agent with MRI. Such agents are not known to bind or combine with proteins or lipids. Gadolinium is a highly effective relaxation agent on surrounding biological fluids or structures and its use has been authorized to provide contrast enhancement when used with MRI in those intracranial lesions with abnormal vascularity or those thought to cause an abnormality in the blood-brain barrier and to facilitate visualization of intracranial lesions including but not limited to tumors. This contrast enhancer is an intravascular agent and cannot cross the blood-brain barrier unless the blood-brain barrier is damaged. It is also authorized for use in the detection of lesions of the spine. It is therefore limited in application, and provides information that is morphological and anatomical, rather than physiological. Potential side effects and adverse reactions exist.
Recently there has been proposed the use of stable neon as a contrast enhancement agent for MRI. This is discussed in U.S. Pat. No. 5,046,498. While the use of stable neon provides certain advantages for contrast enhancement in carrying out MRI, its use has certain limitations. Because neon is not polarizable its use is limited to establishing reverse contrast. Furthermore, neon is not easily soluble in lipids, thus requiring that high concentrations be used and limiting its usefulness to that of a blood pool flow imaging agent due to the administration times that would be required to achieve adequate saturation of the lipid component of tissues, and again only for reverse contrast enhancement.
Accordingly, it is an object of this invention to provide magnetic resonance imaging with improved positive contrast enhancement and with wider applicability over known procedures.
It is another object of this invention to provide a contrast enhancement agent which will enable improved positive contrast enhancement for magnetic resonance imaging and have wider applicability over known contrast enhancement agents.
It is a further object of this invention to provide magnetic resonance imaging with improved contrast enhancement while also obtaining quantitative evaluation of physiology.